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1.
Since just‐in‐time (JIT) has considerable overhead to detect hot spots and compile them at runtime, using sophisticated optimization techniques for embedded devices means that any resulting performance improvements will be limited. In this paper, we introduce a novel static Dalvik bytecode optimization framework, as a complementary compilation of the Dalvik virtual machine, to improve the performance of Android applications. Our system generates optimized Dalvik bytecodes by using Low Level Virtual Machine (LLVM). A major obstacle in using LLVM for optimizing Dalvik bytecodes is determining how to handle the high‐level language features of the Dalvik bytecode in LLVM IR and how to optimize LLVM IR conforming to the language information of the Dalvik bytecode. To this end, we annotate the high‐level language features of Dalvik bytecode to LLVM IR and successfully optimize Dalvik bytecodes through instruction selection processes. Our experimental results show that our system with JIT improves the performance of Android applications by up to 6.08 times, and surpasses JIT by up to 4.34 times.  相似文献   
2.
一种精确程序最坏执行时间分析方法   总被引:1,自引:0,他引:1       下载免费PDF全文
Java语言的动态特性使程序的最坏执行时间分析较悲观和难以预测,提出一种精确最坏执行时间分析方法,在高层分析中,引入一种标记方法,对带有标记的Java类文件进行反编译提取控制流程,得到每一个基本块中的Java 字节码指令的最坏情况下的执行次数,在底层分析中,建立结合流水线和高级缓存影响的时间模型,得到每条指令所对应的执行时间,最后结合高层分析和底层分析的结果得到程序的最坏情况下的执行时间。实验表明,该方法可以使对实时Java 程序的最坏情况执行时间预测更加安全和精确。  相似文献   
3.
This paper describes a new method for code space optimization for interpreted languages called LZW‐CC . The method is based on a well‐known and widely used compression algorithm, LZW , which has been adapted to compress executable program code represented as bytecode. Frequently occurring sequences of bytecode instructions are replaced by shorter encodings for newly generated bytecode instructions. The interpreter for the compressed code is modified to recognize and execute those new instructions. When applied to systems where a copy of the interpreter is supplied with each user program, space is saved not only by compressing the program code but also by automatically removing the unused implementation code from the interpreter. The method's implementation within two compiler systems for the programming languages Haskell and Java is described and implementation issues of interest are presented, notably the recalculations of target jumps and the automated tailoring of the interpreter to program code. Applying LZW‐CC to nhc98 Haskell results in bytecode size reduction by up to 15.23% and executable size reduction by up to 11.9%. Java bytecode is reduced by up to 52%. The impact of compression on execution speed is also discussed; the typical speed penalty for Java programs is between 1.8 and 6.6%, while most compressed Haskell executables run faster than the original. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
4.
Virtual execution environments, such as the Java virtual machine, promote platform‐independent software development. However, when it comes to analyzing algorithm complexity and performance bottlenecks, available tools focus on platform‐specific metrics, such as the CPU time consumption on a particular system. Other drawbacks of many prevailing profiling tools are high overhead, significant measurement perturbation, as well as reduced portability of profiling tools, which are often implemented in platform‐dependent native code. This article presents a novel profiling approach, which is entirely based on program transformation techniques, in order to build a profiling data structure that provides calling‐context‐sensitive program execution statistics. We explore the use of platform‐independent profiling metrics in order to make the instrumentation entirely portable and to generate reproducible profiles. We implemented these ideas within a Java‐based profiling tool called JP. A significant novelty is that this tool achieves complete bytecode coverage by statically instrumenting the core runtime libraries and dynamically instrumenting the rest of the code. JP provides a small and flexible API to write customized profiling agents in pure Java, which are periodically activated to process the collected profiling information. Performance measurements point out that, despite the presence of dynamic instrumentation, JP causes significantly less overhead than a prevailing tool for the profiling of Java code. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
5.
近年来,智能合约中的漏洞检测任务已受到越来越多的关注。然而,缺少源代码和完备的检测特征限制了检测的效果。在本文中,我们提出了DC-Hunter:一种基于字节码匹配的智能合约漏洞检测方案。它可以通过已知的漏洞合约找到类似的漏洞合约,并且可以直接应用于现实世界中的智能合约,无需源码和预先定义的漏洞特征。为了让提出的方法更加切实可行,我们应用程序切片来降低无关代码的影响,通过规范化减少编译器版本带来的差异,并使用图嵌入算法来捕捉函数的结构信息,从而显著减少误报和漏报。此外,借助DC-Hunter我们揭露了一种新型的危险合约。我们发现有一些合约是伪漏洞合约,专门用于诱骗他人尝试进行攻击,从而窃取攻击者的以太币,这种合约称为"蜜罐合约"。我们实现了DC-Hunter的原型,并将其应用于现实世界的智能合约,共有183份危险的合约被报出并确认,其中包括160份漏洞合约和23份蜜罐合约。  相似文献   
6.
基于混合模式的Java卡字节码优化器   总被引:1,自引:0,他引:1       下载免费PDF全文
Java卡是一种基于Java语言的智能卡。因为智能卡的空间和处理器速度的约束,一个应用程序在Java卡上运行时面临的最大问题是存储空间的不足和对程序执行时间的严格限制。因此,对下载到卡中的字节码进行优化是十分必要的。本文提出了一种综合使用扩展指令集和分段压缩算法的Java卡字节码优化器的设计方案,通过对字节码文件的优化,可得到占用空间较少且没有降低执行速率的字节码文件。  相似文献   
7.
Design by Contract is a software engineering practice that allows semantic information to be added to a class or interface to precisely specify the conditions that are required for its correct operation. The basic constructs of Design by Contract are method preconditions and postconditions, and class invariants. This paper presents a detailed design and implementation overview of jContractor, a freely available tool that allows programmers to write “contracts' as standard Java methods following an intuitive naming convention. Preconditions, postconditions, and invariants can be associated with, or inherited by, any class or interface. jContractor performs on-the-fly bytecode instrumentation to detect violation of the contract specification during a program's execution. jContractor's bytecode engineering technique allows it to specify and check contracts even when source code is not available. jContractor is a pure Java library providing a rich set of syntactic constructs for expressing contracts without extending the Java language or runtime environment. These constructs include support for predicate logic expressions, and referencing entry values of attributes and return values of methods. Fine grain control over the level of monitoring is possible at runtime. Since contract methods are allowed to use unconstrained Java expressions, in addition to runtime verification they can perform additional runtime monitoring, logging, and analysis.  相似文献   
8.
分析了Java字节码的解释执行和基于解释执行的Direct Threaded Interpreter性能优化技术.以Direct Threaded Interpreter为基础,提出并实现了一种针对ARM7平台的嵌入式Java虚拟机解释器性能优化方案.对嵌入式Java虚拟机的参考实现、Direct Threaded Interpreter优化方案和新优化方案在ARM7平台上的性能比较表明,所提出的方案优于前两者.  相似文献   
9.
Many modern program verifiers translate the program to be verified and its specification into a simple intermediate representation and then compute verification conditions on this representation. Using an intermediate language improves the interoperability of tools and facilitates the computation of small verification conditions. Even though the translation into an intermediate representation is critical for the soundness of a verifier, this step has not been formally verified. In this paper, we formalize the translation of a small subset of Java bytecode into an imperative intermediate language similar to BoogiePL. We prove soundness of the translation by showing that each bytecode method whose BoogiePL translation can be verified, can also be verified in a logic that operates directly on bytecode.  相似文献   
10.
Java-MaC: A Run-Time Assurance Approach for Java Programs   总被引:2,自引:1,他引:2  
We describe Java-MaC, a prototype implementation of the Monitoring and Checking (MaC) architecture for Java programs. The MaC architecture provides assurance that the target program is running correctly with respect to a formal requirements specification by monitoring and checking the execution of the target program at run-time. MaC bridges the gap between formal verification, which ensures the correctness of a design rather than an implementation, and testing, which does not provide formal guarantees about the correctness of the system.Use of formal requirement specifications in run-time monitoring and checking is the salient aspect of the MaC architecture. MaC is a lightweight formal method solution which works as a viable complement to the current heavyweight formal methods. In addition, analysis processes of the architecture including instrumentation of the target program, monitoring, and checking are performed fully automatically without human direction, which increases the accuracy of the analysis. Another important feature of the architecture is the clear separation between monitoring implementation-dependent low-level behaviors and checking high-level behaviors, which allows the reuse of a high-level requirement specification even when the target program implementation changes. Furthermore, this separation makes the architecture modular and allows the flexibility of incorporating third party tools into the architecture. The paper presents an overview of the MaC architecture and a prototype implementation Java-MaC.  相似文献   
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